Spitfire K.9787.
FUEL CONSUMPTION TESTS IN LEVEL FLIGHT
WEIGHT NORMAL LOAD 5804 lb.

    OPERATIONAL HEIGHT:- 15,000 FT.                              SPECIFIED CRUISING SPEED     -
    WEIGHT BEFORE FLIGHT:- 5804 lb.                                ESTIMATED MEAN WEIGHT:-     -
    TYPE OF FUEL USED:- D.T.D. 230.                                  SPECIFIC GRAVITY OF FUEL AT 60°F:- 0.75
I.C.A.N.
Height
ft.
AIR SPEED
m.p.h.
R.P.M.Boost
Pressure
lb/sq.in.
Mixture ControlConsumption
(S.G. .75)
Statue
Air
Miles
Per Gall.
TrueA.S.I. lb/Hr.Galls/Hr.
 
7000
200184.51770-4.3Auto Weak181   24.1  8.3  
220204.51895-3.0"200   26.658.26
240224   2020-1.6"231   30.8  7.8  
260243.521550  "275.536.757.08
280261.52300+1.9Auto Rich409   54.5  5.14
300280   2440+3.8"466.562.2  4.83
322300   2600+6.0"591   78.8  4.09

                The most economical speed at this height is about 200 m.p.h. A.S.I. and full control of the aeroplane is obtained at this speed.


Spitfire K.9787.
FUEL CONSUMPTION TESTS IN LEVEL FLIGHT
WEIGHT NORMAL LOAD 5804 lb.

    OPERATIONAL HEIGHT:- 15,000 FT.                              SPECIFIED CRUISING SPEED     -
    WEIGHT BEFORE FLIGHT:- 5804 lb.                                ESTIMATED MEAN WEIGHT:-     -
    TYPE OF FUEL USED:- D.T.D. 230.                                  SPECIFIC GRAVITY OF FUEL AT 60°F:- 0.75
I.C.A.N.
Height
ft.
AIR SPEED
m.p.h.
R.P.M.Boost
Pressure
lb/sq.in.
Mixture ControlConsumption
(S.G. .75)
Statue
Air
Miles
Per Gall.
TrueA.S.I. lb/Hr.Galls/Hr.
 
15,000
220179   1975-Auto Weak202   26.9  8.18
240197.52090-3.9"218   29.1  8.26
260214.52220-2.6"242   32.258.06
280232   2345-1.3"277.537.0  7.56
300249   2485+0.3"325.543.4  6.91
317262.52600+1.7"377   50.3  6.3  

                Most economical cruising speed is approximately 200 m.p.h. A.S.I. At this speed the aeroplane is fully controllable.


HANDLING TRIALS.

1. Cockpit.
 
(i) Ease of entry and comfort - The cockpit is easy to enter and leave and is comfortable and roomy. There is, however, insufficient head clearance for a tall pilot. There is no undue noise. There is sufficient heating to keep the cockpit warm at high altitudes. The comfort would be greatly improved by the introduction of foot rests for use when flying "feet off" the rudder, and an arm rest for the left arm. The seat becomes very hard after long periods in bumpy conditions.
 
(ii) View - The view forwards and to the rear is fair, and upwards is good. The windscreen distortion complained of on the prototype is not considered serious nor does it effect the landing in any way.
 
(iii) Controls - All controls work freely and without undue friction on the ground. There is full movement of all controls obtainable when a large pilot in flying kit is seated in position. The tail trimming wheel is situated on the left, and an electric indicator on the dashboard gives the extent of trim. The rudder bias is controlled by a smaller hand wheel also on the left but there is no indicator. Some indicator should be fitted to show when the control is central. No means of lateral trim is provided. The flaps are operated pneumatically by a lever on the dashboard with an indicator next to it. The undercarriage is raised and lowered by selector lever and hand operated pump situated on the right. The hand lever is very close to the oxygen bayonet fitting so that a pilot with a large hand might cut himself. The Klaxon warning horn, which was previously reported to be not loud enough, is now satisfactory. A space for pilot's miscellaneous articles should be provided.
 
(iv) Seat adjustment and straps - The seat is fully adjustable by means of a lever on the right. Sutton harness is provided and this is long enough to fit over a large pilot fully dressed. There is a release provided for free movement.
 
(v) Brakes - The brakes are operated by the Dunlop system and are actuated by a lever situated at the top of the control column. A locking devise for parking is provided. The pressure gauge is situated on the dashboard.
 
(vi) Instruments - The general layout is good. In the centre of the dashboard is a standard blind-flying panel. The engine instruments are grouped to the right of this, and on the left are subsidiary indicators such as:- tail trim, flaps, brake pressures, etc. Under the blind-flying panel, and forward of the control column, is mounted a P.6 type compass. This is easy to read as are all other instruments.
 
(vii) Emergency exits - No exit is provided other than the normal means consisting of a shall hinged side panel. This side panel cannot be opened when the sliding hood is closed so that it is advisable for the pilot to open the hood before attempting to land. A strong-point is provided immediately behind the pilot's head, and it is possible for the pilot to squeeze through the side panel with the aircraft overturned. At high speeds the hood cannot be opened with one hand. It is recommended that the release be modified to enable this to be done.
 
2. Handling and Flying Qualities.
 

                The aeroplane has been flown at the following loadings and positions of gravity:-

Load forWeight (lb.)C.G. Position
(inches aft of datum)
Typical service load58197.7
Extended aft.58198.6
Forward limit53385.8

                Unless otherwise stated the following remarks apply to all three cases.

(i) Ground handling - The aeroplane has been handled satisfactorily on the ground in winds up to 20 m.p.h. The brakes are easy to operate. They work smoothly and progressively and the differential action is good.
 
(ii) Take-off - The take-off is poor but is easily executed. There is a tendency to swing to the left but this is easily overcome by opposite rudder.
 
(iii) Climb - The initial climb is poor until the aeroplane gathers speed. The best climbing speed is 175 m.p.h. There is insufficient rudder bias for climbing "feet off" so that assessment of the directional stability is difficult but the aeroplane is stable. The aeroplane is laterally stable on the climb, but is only stable longitudinally with centre of gravity forward. The undercarriage, which retracts in about 10 seconds, is satisfactory.
 
(iv) Controls in level flight - The ailerons become excessively heavy above cruising speed. Tests have been made on Spitfire K.9793 with modified "flush strung" ailerons, and these have given a definite improvement in speeds up to 340 m.p.h. A.S.I. Beyond this speed, the modified ailerons also became very heavy and "ballooning" of the fabric at the trailing edge was noticed. A further aileron modification, introducing intermediate ribs, is being made and tests will shortly be made with these modified ailerons.

               The rudder and elevators are light, quick in response, and effective and are satisfactory. In general the heaviness of these controls increases with speed.
 

(v) Stability - The aircraft is laterally stable at all speeds except in the immediate vicinity of the stall when it is unstable. The aircraft is directionally stable engine 'OFF' and 'ON' at all speeds, but on the climb this is difficult to assess owing to insufficient rudder bias. Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'. Longitudinal stability records are attached.
 
(vi) Stalls - Stalling speed (flaps and undercarriage up) 64 m.p.h. A.S.I.
            Stalling speed (flaps and undercarriage down) 58 m.p.h. A.S.I.

               At the stall there is considerable aileron snatch. A wing tends to drop but can be held up with aileron. Recovery is immediate as the control column is moved forward. Warning of the approach to the stall is given by vibration and buffeting as well as by the high attitude of the nose. The control column at the stall is just aft of central.
 

(vii) Control and stability at the stall - The aeroplane has been put through the tests required under A.D.M.293.

(a) Flaps and undercarriage up - Trimmed to glide at 1.2 times stalling speed, the aeroplane is longitudinally unstable. Turns can be made down to 70 m.p.h. A.S.I. in either direction and recovery can be made with either rudder or ailerons held fixed. With the control column right back, the aeroplane can be held in a straight path for a few seconds only by the careful use of rudder and ailerons. It then pitches and tries to go into a diving turn in either direction, but this can be checked by the use of rudder when a "falling leaf" results. There is no tendency to spin.
 
(b) Flaps and undercarriage down - Trimmed to glide at 1.2 times stalling speed, the aeroplane is longitudinally unstable. Turns can be made down to 60 m.p.h. in either direction when the behaviour of the aeroplane is similar to that with flaps and undercarriage up. With the stick right back, and the rudder held central, the aeroplane goes into a diving turn but there is no tendency to spin.

(viii) Landing - The aeroplane is easy to land. The best approach speed is 85 m.p.h. A.S.I. There is ample elevator available so that it is not necessary to have the control column right back when landing. If the engine is opened up suddenly with flaps and undercarriage set for landing, the aeroplane becomes tail heavy but can be held until retrimmed. The resultant climb away is poor.

3. Acrobatics.
 
                Loops, half rolls off loops, and slow rolls have been done. These manoeuvres are easy to make and the aeroplane behaves quite normally in all of them.
 
4. Comparison with Prototype.
 
                The aeroplane does not differ in marked degree from the prototype reported on in A. & A.E.E. Report M/692/Int.2. dated September 1936.

                The greatest difference is the modified ailerons which are not yet in their final state.

                It was reported that the rudder bias on the prototype was adequate throughout the speed range. It has been found that the rudder bias on production aircraft is insufficient for the climb. Since there is adequate bias for gliding, however, it is possible that the condition for the climb might be improved by moving the effective travel of the gear so as to give increased movement for climbing and decreased movement for gliding. This arrangement has not yet been tried at this establishment.

                The gearing of the elevator control and elevator trimmers which were considered too high in the prototype are satisfactory in this aeroplane.

                The range of the landing flaps has been increased to 90° as suggested and the landing qualities are thereby improved.

                The windscreen has not been modified and the distortion complained of in the prototype is present in this aeroplane, though, as stated above, it is not important.


Centre of Gravity Diagram    Stability Records

[WWII Aircraft Performance] [Spitfire Mk I]